Equine Infectious Anemia Virus (EIAV), the pathogen of Equine Infectious Anemia, was the first kind of virus discovered by human. Equine Infectious Anemia, first described in France in 1843, has caused tremendous economic loss in animal husbandry for over one century. Scientists all over the world have been making efforts to investigate techniques to control this disease. Since the 1960s, the Chinese government has provided extraordinary financial support to fund studies on the biological and immunological properties of EIAV. During their investigations, Chinese scientists isolated a virulent strain that was quite different from strains isolated in other countries. Through passage on donkey luekocyte for many generations, this virulent strain was successfully attenuated. Using this attenuated virus as a vaccine strain, inoculated animals developed persistent and strong immunity against EIAV and were protected against Equine Infectious Anemia. The vaccine has been prepared in large scale since 1976 and used nation-wide since 1978. More than 70 million horses, mules, and donkeys have been vaccinated and Equine Infectious Anemia has been successfully controlled in China (Rongxian Shen, et al. Study on immunological methods of Equine Infectious Anemia, China Agricultural Science, vol. 4, 1–15, 1979).
EIAV is classified as a lentivirus of the Retroviridae family. In many aspects, such as its genomic organization, functional proteins and the regulatory mode of gene expression, EIAV shows great similarity to Human Immunodeficiency Virus (HIV), another lentivirus which is the cause of AIDS. (J. M. Coffin, The structure And Classification of Retroviruses, The Retroviridae, Vol. 1, p 19, edited by Jay A. Levy, Plenum Press). Moreover, there are extensive homologies in structure and function of reverse transcriptase, proteinase, envelope glycoprotein, and nucleoprotein between EIAV and HIV. Horses infected with EIAV manifest symptoms typical of lentiviral infection, including periodical fever, anemia with the decrease of erythrocytes and durative viremia. Thus, EIAV may serve as an important research model in investigating the infection mechanisms and the enzymatic functions of other lentiviruses (R. C. Montelaro et al, Equine Retroviruses, in: vol. 2, p 257).
With the development and widespread application of molecular biology since the 1970s, the genomic organization of EIAV has been intensively studied. Full-length genome sequences of EIAV from the standard (reference) virulent strain isolated in the USA (Wyoming strain), from another isolate in Japan (Goshum strain), and from several cell culture-adapted strains have all been registered in GenBank. None of these, however, are vaccine strains. Currently, the EIAV donkey leukocyte attenuated vaccine strain that was developed in China remains the only lentivirus vaccine strain in the world. It has been used in large scale and has been proven to be effective and safe over a long period of application (R. C. Montelaro, et al. in: Vaccine against Retroviruses, Vol. 4, P 605; R. C. Montelaro, et al. Equine Retroviruses, in: Vol. 2, P 257). The genomic sequence and organization of the EIAV vaccine strain has not been previously characterized. The characterization of the EIAV vaccine strain genomic sequence and structure will not only lay the foundation for refining the vaccine and preparing new genetic engineering EIAV vaccines, but also, more importantly, may provide a model for developing other lentivirus vaccines.
Therefore, the objects of the invention are to provide the full-length genomic sequence of the EIAV vaccine strain adapted to donkey leukocyte; the sequences of each functional genes and their putative amino acid sequences; and uses of these genes and their expression products.